The classical adjoint

AbstractThis paper summarizes the historical background of the notion of the classical adjoint as outlined by Muir, and provides applications of the adjoint to various studies of generalized invertibility of matrices over commutative rings. Specifically, in this setting, the classical adjoint is used to provide a novel proof of von Neumann’s 1936 observation that every matrix over a regular ring is regular, and to provide a necessary and sufficient condition for the existence of the Moore–Penrose inverse of a given matrix. In particular, a representation of the Moore–Penrose inverse is given that leads to an immediate proof of Moore’s 1920 formula specifying the entries of his “reciprocal” in terms of determinants

Perioperative goal-directed therapy - What is the evidence?

Perioperative goal-directed therapy aims at optimizing global hemodynamics during the perioperative period by titrating fluids, vasopressors, and/or inotropes to predefined hemodynamic goals. There is evidence on the benefit of perioperative goal-directed therapy, but its adoption into clinical practice is slow and incomprehensive. Current evidence indicates that treating patients according to perioperative goal-directed therapy protocols reduces morbidity and mortality, particularly in patients having high-risk surgery. Perioperative goal-directed therapy protocols need to be started early, should include vasoactive agents in addition to fluids, and should target blood flow related variables. Future promising developments in the field of perioperative goal-directed therapy include personalized hemodynamic management and closed-loop system management. (C) 2019 Elsevier Ltd. All rights reserved

Intraoperative hypotension and its prediction

Intraoperative hypotension (IOH) very commonly accompanies general anaesthesia in patients undergoing major surgical procedures. The development of IOH is unwanted, since it is associated with adverse outcomes such as acute kidney injury and myocardial injury, stroke and mortality. Although the definition of IOH is variable, harm starts to occur below a mean arterial pressure (MAP) threshold of 65 mmHg. The odds of adverse outcome increase for increasing duration and/or magnitude of IOH below this threshold, and even short periods of IOH seem to be associated with adverse outcomes. Therefore, reducing the hypotensive burden by predicting and preventing IOH through proactive appropriate treatment may potentially improve patient outcome. In this review article, we summarise the current state of the prediction of IOH by the use of so-called machine-learning algorithms. Machine-learning algorithms that use high-fidelity data from the arterial pressure waveform, may be used to reveal 'traits' that are unseen by the human eye and are associated with the later development of IOH. These algorithms can use large datasets for 'training', and can subsequently be used by clinicians for haemodynamic monitoring and guiding therapy. A first clinically available application, the hypotension prediction index (HPI), is aimed to predict an impending hypotensive event, and additionally, to guide appropriate treatment by calculated secondary variables to asses preload (dynamic preload variables), contractility (dP/dt(max)), and afterload (dynamic arterial elastance, Ea(dyn)). In this narrative review, we summarise the current state of the prediction of hypotension using such novel, automated algorithms and we will highlight HPI and the secondary variables provided to identify the probable origin of the (impending) hypotensive event

Which type of fluid to use perioperatively?

Fluid administration in the perioperative period is daily clinical practice for all anesthesiologists. The goal of fluid administration is to increase cardiac output in order to ultimately improve oxygen delivery to the tissues. Fluid therapy can be given as maintenance or as replacement fluid therapy. For both of these therapies balanced crystalloids belong to the first line of treatment. Colloids are used for fluid replacement as well, but are given for more specific indications such as hypovolemia as a consequence of blood loss. Fluids, as any other intravenous drug, have indications, contra-indications, and potential side-effects. No conclusive evidence exists over the way and amount of fluids that should be administered, and several strategies have been developed, e.g., restrictive or liberal fluid therapy or perioperative goal-directed therapy (PGDT). Restrictive fluid therapy uses limited amounts of fluid compared to liberal fluid therapy, however no clear definitions of restricted or liberal fluid therapy are available. PGDT uses hemodynamic variables to assess fluid responsiveness and to guide fluid therapy in order to optimize the hemodynamic status of the patient. Future directions in fluid administration are to use personalized hemodynamic target values and to use PGDT in closed-loop systems. Most important, fluids should be administered with the same caution that is used with any intravenous drug

Perioperative Hemodynamic Monitoring:An Overview of Current Methods

Perioperative hemodynamic monitoring is an essential part of anesthetic care. In this review, we aim to give an overview of methods currently used in the clinical routine and experimental methods under development. The technical aspects of the mentioned methods are discussed briefly. This review includes methods to monitor blood pressures, for example, arterial pressure, mean systemic filling pressure and central venous pressure, and volumes, for example, global end-diastolic volume (GEDV) and extravascular lung water. In addition, monitoring blood flow (cardiac output) and fluid responsiveness (preload) will be discussed